Acidity-Basicity Data (pKa Values) in Nonaqueous Solvents

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The highlighted papers contain large amounts of data (acids – red, bases – blue, both acids and bases – purple)

Publication

Data

Medium

Method

Description

Available files

Angew. Chem. Int. Ed. 2014, 53, 1435-1438

pKa values

THF

UV-Vis Spectrophotometry

Synthesis and basicity of new organosuperbases, N,N’-bis(imidazolyl)guanidine bases (BIG bases), is reported. Their pKa values, determined as 26.1–29.3 in tetrahydrofuran, reach higher than any of the following superbases: DBU, TBD, TMG (tetramethylguanidine), Verkade’s base, Schwesinger’s P1-phosphazenes (t-BuP1, EtP1, MeP1, …), or even the guanidino-phosphazenes. They are probably the strongest known phosphorous-free neutral organic bases both in solution and in the gas phase.

pKa values in THF and some other properties of the BIG superbases (PDF)

pKa values in THF of some common superbases: TMG, tBuP1(pyrr), TBD, Verkade’s base, guanidino-phosphazene HP1(tmg) (PDF)

J. Phys. Org. Chem. 2014, 27, 676–679

gas-phase acidity (GA) values

gas phase

FT-ICR, quantum chemistry (DFT B3LYP 6-311+G**)

The gas-phase acidity (GA) values were determined (using the FT-ICR equilibrium method) for a number of perfluoroalkyl-substituted sulfonylimides, e.g. Tf2NH (bis-trifyl-imide), (C2F5SO2)2NH, (C4F9SO2)2NH and others. The GA scale below (CF3SO2)2NH  (bis-trifylimide, GA = 286.5 kcal mol-1) was extended and partially revised. The GA value of (C4F9SO2)2NH, which is currently the strongest acid was revised from 284.1 to 278.6 kcal mol-1.

Gas-phase acidities of of perfluoroalkyl-substituted sulfonylimides (PDF)

Angew. Chem. Int. Ed. 2013, 52, 11569-11572

pKa values

Acetonitrile

UV-Vis Spectrophotometry

MeCN pKa values of Chiral Brønsted Acid Catalysts (organocatalysts) of the following types: BINOL-phosphoric acids, NTPA (N-trifylphosphoramide) and sulfurylimides (JINGLE, BINOL-bis(sulfurylimide)).

pKa values in acetonitrile of chiral Brønsted acid catalysts (BINOL, NTPA and JINGLE derivatives) (PDF)

Chem. Sci, 2013, 4, 2788-2796

pKa values

Acetonitrile, 1,2-Dichloroethane

UV-Vis Spectrophotometry

Basicity (pKa values) of a number of triaryl phosphines (phosphanes) (metal-free hydrogen activation catalysts), most of them derivatives of triphenylphosphine (triphenylphosphine). The rate of hydrogenation is strongly dependent on the electronic nature of the phosphine and of the acidity of the corresponding phosphonium cation. A careful balance of these two factors provides highly efficient metal-free hydrogenation catalysts.

Basicity constants (pKa values) of phosphines catalysts in acetonitrile and 1,2-dichloroethane (PDF)

J. Phys. Org. Chem. 2013, 26, 162-170.

pKa values, gas-phase acidity values

Acetonitrile, Water, 1,2-Dichloroethane, Gas phase

UV-Vis Spectrophotometry, FT-ICR, quantum chemistry (DFT B3LYP 6-311+G**), COSMO-RS, SMD

Acidities (pKa) of a number of different acids including the well-known superacids trifluoromethanesulfonic (triflic) acid, HBr, HI, bis-trifylimide (Tf2NH), etc as well as weaker acids (HCl, acetic acid, phenol) etc are presented in media of different physical and chemical nature: water, acetonitrile (AN, MeCN), 1,2-dichloroethane (DCE) and the gas phase, with special emphasis on strong acids. Dependence of the acidity trends on moving from water to the gas phase on the nature of the acidity centre and the molecular structure are analyzed. The acidity orders are different in water, AN, DCE and the gas phase. It is demonstrated that the decisive factor for behavior of the acids when transferring between different media is the extent of charge delocalization in the anion and that the recently introduced WAPS parameter in spite of its simplicity enables interpretation of the trends in the majority of cases.

pKa values (scheme) in water, acetonitrile, dichloroethane and gas-phase acidities (PDF)

 

Table of pKa values in water, acetonitrile, 1,2-dichloroethane and gas phase (PDF)

Chem. Eur. J. 2012, 18, 3621 – 3630

pKa values, gas-phase basicities

MeCN, gas phase

UV-Vis Spectrophotometry

A New Class of Organosuperbases – N-Alkyl-1,3-dialkyl-4,5-dimethylimidazol-2-ylidene Amines (imidazolidine ylidene amines) – is presented that by the base strength (pKa values, gas-phase basicities) reaches higher than the common organosuperbases DBU, TMG or the Schwesinger P1 phosphazenes.

pKa table of Superbases in acetonitrile (PDF)

Eur. J. Org. Chem. 2012, 2167-2172

pKa values

Acetonitrile

UV-Vis Spectrophotometry

Basicity (pKa values) of a number of phosphanes (phosphines) – both monophosphanes (monophosphines) and diphosphanes (diphosphines, common ligands in catalysts) – and amines in MeCN. Compounds: triphenylphosphine, trimethylphosphine, bis-diphenylphosphinoethane, bis-diphenylphosphinopropane, BINAP, BIPHEP, etc. The possibility of intramolecular hydrogen bond formation in protonated diphosphines is assessed.

Table of pKa values in acetonitrile (PDF)

"Design and acidity measurements of superacidic molecules", presented at ESOR XIII Tartu, on 14.09.2011

pKa values, gas-phase acidity values

MeCN, 1,2-dichloroethane, gas phase

Spectrophotometry, FT-ICR, quantum chemistry (DFT B3LYP 6-311+G**)

An overview was given about the principles of design and acidity measurement of superacids (superacidic molecules), illustrated by numerous acidity data.

Full talk (PDF)

Chem. Eng. J. 2011, 171, 794-800

pKa values

MeCN

COSMO-RS (and some experimental from different sources)

pKa values of different CO2-binding organic liquids (CO2BOLs) have been calculated (using COSMO-RS) or collected from the literature and related to the performance of the CO2BOLs in CO2 capture.

pKa table in acetonitrile (PDF)

J. Org. Chem. 2011, 76, 391-395

pKa values

1,2-dichloroethane (also acetonitrile)

Spectrophotometric

Relative acidities of 64 strong acids (some of them superacids) in 1,2-dichloroethane and 54 strong acids in acetonitrile. Included are numerous sulfonimides, cyanocarbon acids and well-known mineral acids, such as HCl, HBr, HI, H2SO4, HNO3, HBF4, CF3SO3H, FSO3H, HClO4, (CF3SO2)2NH (Tf2NH) and (C2F5SO2)2NH. Contains some pKa values of acid catalysts.

Table of pKa values in 1,2-dichloroethane (with estimated values in MeCN) (PDF)

 

Table of pKa values in MeCN (PDF)

J. Phys. Chem. A 2010, 114, 10694-10699

Gas-phase basicity values

Gas phase

FT-ICR, quantum chemistry (W1, G2)

Gas-phase basicity values for weak bases: CS2, water, FCN, C2H4, CF3CN, (CF3)2CHOH, F2NH, CF3CHO, C6F6, CH3Cl, (CF3)3COH, CF3COCl, (CN)2, FSO2Cl, SO2, (CF3)2CO, COS, F2CO, CF3CCH, (CF3)2O and SO2F2. The assigned values have been obtained by combining and critically evaluating data from multiple experimental and theoretical sources and are thus expected to be highly reliable.

Table of gas-phase basicity (GB) values, ladder of GB measurements, correlations between GB values from different sources (PDF)

Angew. Chem. Int. Ed. 2010, 49, 6885-6888.

Absolute acidity values

Acetonitrile, DMSO, water, benzene, etc.

Computations using the rCCC model

On the basis of the absolute chemical potential of the proton, a unified absolute pH scale is introduced that is universally applicable in the gas phase, in solution, and in the solid state. With this scale it is possible to directly compare acidities in different media and to give a thermodynamically meaningful definition of superacidity.

Table of available acidity ranges in selected solvents (PDF)

J. Phys. Chem. A 2009, 113, 8421-8424

pKa values and Gas-phase acidity values

Acetonitrile, gas phase

Spectrophotometric, FT-ICR, G3(MP2), DFT B3LYP 6-311+G**

Gas-phase acidity and pKa values in MeCN for a number of aromatic sulfonimides, fluorinated aliphatic sulfonimides, including Tf2NH and (C2F5SO2)2NH, and some other acids. The work presents revision of the gas-phase acidity (GA) scale from (CF3CO)2NH to (C2F5SO2)2NH, i.e. about a 24 kcal mol-1 range of gas phase acidities and ends the controversy between experiment and computations in this acidity range.

Table of experimental and computational gas-phase acidities and pKa values in acetonitrile (PDF)

J. Comp. Chem. 2009, 30, 799-810

pKa values

Acetonitrile

Spectrophotometric

Experimental pKa values of more than 200 neutral acids in acetonitrile (from our group and from other authors) ranging from pKa 3.6 to 29.

Acids: alcohols, carboxylic acids (acetic acid, trifluoroacetic acid, benzoic acid, different diacids, e.g. phthalic acid, oxalic acid, succinic acid), phenols (nitrophenols, chlorophenols, 2,4-dinitrophenol, 2,4,6-Trinitrophenol (picric acid), etc), sulfonic acids (para-toluene sulfonic acid, substituted benzenesulfonic acids), anilines, sulfonamides, phenylmalononitriles, diphenylacetonitriles, strong acids (perchloric acid, fluorosulfuric acid, methanesulfonic acid, 4-toluenesulfonic acid) acid catalysts, etc.

The work aims at computational (COSMO-RS) estimation of MeCN pKa values and the experimental values of our group are used as fit data set and values from other authors as test data set.

Tables of pKa values (PDF)

J. Org. Chem. 2008, 73, 2607-2620

pKa values and Gas-phase acidity values

Acetonitrile, DMSO, Water, gas phase

Spectrophotometric, FT-ICR, DFT B3LYP 6-311+G**

Gas-phase acidity and pKa values for a number of poly-CF3-substituted aromatic compounds. Included are (CF3)5Phenol, (CF3)5Aniline, (CF3)5Toluene and (CF3)5Phenylmalononitrile.

Table of experimental pKa values and Gas-phase acidities (PDF)

Chem. Eur. J. 2007, 13, 7631-7643

pKa values and Gas-phase basicity values

Acetonitrile, Tetrahydrofuran, gas phase

Spectrophotometric, FT-ICR, DFT B3LYP 6-311+G**

Gas-phase basicity and pKa values for a number of diamines and related monoamines.

Included are different substituted diamines: 1,3-propanediamine (1,3-diaminopropane) and its derivatives, tetramethylated 1,2-ethanediamine (1,2-diaminoethane) and 1,4-butanediamine (1,4-diaminobutane), piperidine, piperazine, bispidine, dimethylbispidine.

Schemes of base structures, table of pKa and gas-phase basicity values (PDF)

"Brønsted Acidity of Neutral and Cationic Acids in Nonaqueous Solvents: Recent Developments", (INOR 1036) presented at the ACS Spring meeting Mar 27, 2007, Chicago

pKa values

Acetonitrile, Heptane, 1,2-Dichloroethane, THF, gas phase

spectrophotometric, FT-ICR

This is a poster summarizing the Brønsted acidity and basicity data gathered by our group during the recent years.

Full poster (PDF)

J. Phys. Chem. A 2007, 111, 1245-1250

Gas-phase basicity values

gas phase

FT-ICR, spectrophotometric

Gas-phase basicity for 30 superbases: phosphazene superbases: P2-phosphazenes (EtP2, PhP2, …), P1-phosphazenes (t-BuP1, EtP1, MeP1, …), BEMP superbase; MTBD, ETBD, ITBD, Verkade's superbases

Scheme of base structures, table gas-phase basicity values (PDF)

Anal. Chim. Acta. 2006, 566, 290-303

Uncertainty

MeCN

 

Spectrophotometric

 

Uncertainty estimation in measurement of pKa values in nonaqueous media (solvents) using two different approaches.

Table of pKa values, experimental measurement results and uncertainty values (PDF)

J. Org. Chem. 2006, 71, 2829-2838

pKa values
of acids

 

Acetonitrile

 

Spectrophotometric

 

pKa values of 93 neutral acids in acetonitrile ranging from pKa 3.7 to 28.1.

Acids: alcohols, carboxylic acids (acetic acid, benzoic acid), phenols (2,4-dinitrophenol, picric acid, etc), sulfonic acids (para-toluene sulfonic acid, substituted benzenesulfonic acids), anilines, sulfonamides, phenylmalononitriles, diphenylacetonitriles, etc.

Titrants: trifluoromethanesulfonic acid (triflic acid) and phosphazenes t-BuP1(pyrr) and EtP2(dma)

Table of pKa values and experimental measurement results (PDF)

J. Org. Chem. 2006, 71, 7155-7164

pKa values

 

Acetonitrile

 

Spectrophotometric

 

Acetonitrile pKa values of 10 substituted bispidine bases.

Table of bispidine structures and table of pKa measurement results (PDF)

J. Am. Chem. Soc. 2005, 127, 17656-17666

pKa values

 

GPB, PA

Tetrahydrofuran

 

Calculation

Spectrophotometric

 

DFT B3LYP

6-311+G**

pKa values of a number of organosuperbases – phosphazene bases, guanidinophosphazenes and related bases – have been determined.

Table of pKa values of te superbases and experimental measurement results and table of results of basicity calculations (PDF)

J. Org. Chem. 2005, 70, 1019-1028

pKa values
of bases

Acetonitrile

Spectrophotometric

pKa values of 89 neutral bases in acetonitrile ranging from 4-Cl-2-NO2-Aniline (pKa = 3.80) to 4-MeO-C6H4-N=P(N=P(Nme2)3)(Nme2) (pKa = 31.99).

Among the bases are: phosphazene superbases, DBU, TBD, MTBD superbase, proton sponge, triethylamine, pyrrolidine (and other substituted amines) pyridine and substituted pyridines (DMAP, etc), aniline and substituted anilines.

Table of pKa values and experimental measurement results (PDF)

J. Org. Chem. 2003, 68, 9988-9993

pKip, pKa values

 

GPB

Tetrahydrofuran

Spectrophotometric

 

FT-ICR spectrometric

pKa and pKip values of 31 bases in tetrahydrofuran ranging from 4‑CF3-C6H4-P1(pyrr) (pKa = 14,6) to 2‑Cl‑C6H4‑P4(pyrr) (pKa = 26,6). Gas-Phase basicities of 10 bases.

Tables of pKip, pKa and GBP values and experimental measurements results (PDF)

J. Org. Chem. 2003, 68, 7795-7799

pKip values

Heptane

Spectrophotometric

Relative pKip values of 21 weak acids in heptane.

Table of pKip values and experimental measurements results (PDF)

J. Chem. Soc., Perkin Trans. 2. 2002, 1950-1955

pKa values

Acetonitrile

Spectrophotometric

Acetonitrile pKa values of some amides and imidines of benzoic acid. The acidifying effect of the substituent =NSO2CF3.

pKa table and experimental measurements results (PDF)

Inorg. Chim. Acta. 2002, 340, 87-96.

pKa table

Acetonitrile

Spectrophotometric

pKa values for neutral and cationic bases in MeCN. Used a different calculation method to get also pKa values of cationic bases.

pKa table and experimental measurements results (PDF)

J. Org. Chem. 2002, 67, 1873-1881

pKip, pKa values

Tetrahydrofuran

Spectrophotometric

pKa and pKip values of 45 bases in tetrahydrofuran ranging from 2-MeO-Pyridine (pKa = 2,6) to EtP1(pyrr) (pKa = 21,5).

Among the bases are: various phosphazene superbases (incl. several Schwesinger's phosphazenes), DBU, TBD, TMG, pyridine, aniline, etc.

Table of pKip and pKa values, experimental measurements results and Table with AN pKa and literature values (PDF)

J. Chem. Soc., Perkin Trans. 2. 2001, 229-232

pKa values

 

GPA

Dimethyl

sulfoxide

Potentiometric

 

FT-ICR spectrometric

The acidifying effect of the substituent =NSO2CF3 on the acidity of derivatives of benzenesulfonamide and toluene-p-sulfonamide in the gas phase and in dimethyl sulfoxide (DMSO)

The GPB and DMSO pKa values of toluene-p-sulfonamide (PDF)

J. Org. Chem. 2000, 65, 6202-6208

pKa table

MeCN

Spectrophotometric

pKa values of 29 bases in acetonitrile ranging from Pyridine (pKa = 12,33) to DBU (pKa = 24,13)

Table of pKa values and experimental measurement results (PDF)

J. Chem. Soc., Perkin Trans. 2. 2000, 1125-1133

pKa values

 

GPA-s

Dimethyl

sulfoxide

Potentiometric

 

FT-ICR spectrometric

Comparison of Brønsted acidities of neutral CH-acids in gas phase and dimethyl sulfoxide. A voluminous acidity table in DMSO and gas phase (Fluorene, indene, cyclopentadiene, fluoradene, …).

Acidity table (table of pKa values) in dimethyl sulfoxide and GPB (PDF)

J. Org. Chem. 1998, 63, 7868-7874

pKa table

Acetonitrile

Spectrophotometric

pKa values (dissociation constants) of 36 acids in acetonitrile ranging from 4-Cl-C6H4-SO(=NTf)-NH-SO2-C6H4-4-NO2 (pK = 3,75) to 2,4-dinitrophenol (pK = 16,66)

Table of dissociation constants (pKa values) in acetonitrile and experimental measurement results (PDF)

J. Org. Chem. 1997, 62, 8479-8483

pKip values

Heptane

Spectrophotometric

Relative pKip (acidity constants) values of 6 weak acids in heptane.

Table of pKip values and experimental measurements results (PDF)

 

Comments

Should you have any questions regarding the data, the used experimental, data treatment or computational methods, etc, please do not hesitate to contact Ivo Leito (e-mail: ivo.leitobwut.ee)!     Proposals for collaboration in pKa measurement are also most welcome!

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